1. Field of the Invention
The present application relates generally to a semiconductor device and method of producing the same.
2. Description of the Related Art
Semiconductor devices, particularly integrated circuits using MOS transistors have increasingly been highly integrated. MOS transistors in integrated circuits have been downsized to nano sizes as the integration level is increased. The basic circuit of digital circuits is an inverter circuit. As MOS transistors constituting an inverter circuit are downsized, problems occur such as difficulty in leaking current control, reduced reliability due to hot carrier effect, and difficulty in reducing the area occupied by circuits while assuring the necessary current quantity. In order to resolve these problems, surrounding gate transistors (SGT) have been proposed in which the source, gate, and drain are provided on a substrate in the vertical direction and the gate surrounds an island-shaped semiconductor, and CMOS inverter circuits using SGTs have been proposed (for example, see S. Watanabe, K. Tsuchida, D. Takashima, Y. Oowaki, A. Nitayama, K. Hieda, H. Takato, K. Sunouchi, F. Horiguchi, K. Ohuchi, F. Masuoka, H. Hara, “A Nobel Circuit Technology with Surrounding Gate Transistors (SGTs) for Ultra High Density DRAMs,” IEEE JSSC, Vol. 30, No. 9, 1995).
An inverter is constructed using a pMOS transistor and an nMOS transistor. The mobility of holes is half the mobility of electrons. Therefore, the pMOS transistor must have a gate width double the gate width of the nMOS transistor in an inverter circuit. For this reason, a conventional CMOS inverter circuit using SGTs comprises two pMOS SGTs and one nMOS SGT. In other words, a conventional CMOS inverter circuit using SGTs comprises three island-shaped semiconductors.